Computed tomography is known in the art. By one approach, sometimes referred to as third generation computed tomography, a fan beam or a cone beam facilitates the gathering of object data while the object being scanned and the X-ray source/detector rotate with respect to one another. In general, these approaches entail the capture and processing of data as corresponds to a relatively large number of rotationally differentiated views.
In practice, a number of practical limitations can make it difficult to properly interpret such data. As one example, a given detector array may be comprised of a plurality of discrete elements that are not necessarily all exactly equally spaced apart. As another example, and particularly when using curved detector arrays, focus issues can become problematic. Therefore, for these and other reasons, it may be useful and/or necessary to calibrate a given X-ray source/detector platform from time to time to attempt to minimize such problems.
Such calibration, however, can present unwanted issues in and of itself. A calibration exercise typically represents downtime for the platform; that is, the platform cannot be used for real tasks while being calibrated. Furthermore, in at least some cases, calibration does not necessarily assure that the platform is now assured of providing useful results. For example, calibration usually entails use of a calibration object (such as a metal pin). The form factor and weight of this calibration object will often differ from that of a real object of interest. This, in turn, can lead to different interactions between the real object of interest and the platform than as are experienced by the calibration object (for example, a rotating turntable may tilt slightly when supporting a large real object of interest as compared to when supporting a calibration object). In other cases, the pin itself may be quite tall (when calibrating, for example, a tall scanning apparatus). In such a case, centrifugal force can cause considerable wobbling of the pin. Such undesired movement, of course, can also impact calibration accuracy and/or calibration time requirements.
The prior art, then, presents a troubling conundrum. Scanning results can be unreliable or at least less useful in the absence of calibration. At the same time, calibration itself is often viewed as an unproductive activity to be avoided if possible, and one that may not lead in any event to a reliably conducted scanning process.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.